Quite a few have speculated about a connection between the Nazi and Soviet actions - even though a direct connection is unlikely, the coincidence in timing is striking enough, as are the patterns of NKVD-Gestapo cooperation at this time.
Interesting, other than the timing what other evidence is there "of NKVD-Gestapo cooperation"? In an interesting parallel in the 1970s and 80s the intel. services of the South American dictatorships cooperated in Operation Condor to the extent they at times killed each others' dissidents.
http://en.wikipedia.org/wiki/Operation_Condor